Cryogenic Bandgap Reference Circuit With Compact Model Parameter Extraction of MOSFETs and BJTs for HPGe Detectors

This article presents the development of a cryogenic bandgap reference (BGR) circuit in a standard 0.18- $\mu \text{m}$ CMOS process for high-purity germanium (HPGe) detectors for low-background physics experiments. It provides a temperature-independent reference for mixed-signal circuits such as a ramp generator. A reliable cryogenic model is essential for the circuit design. The parameters of metal–oxide–semiconductor field-effect transistors (MOSFETs) and bipolar junction transistors (BJTs) were characterized and extracted at cryogenic temperatures from dc measurements on various geometries. MOSFETs had a general increase in threshold voltage and carrier mobility, a decrease in subthreshold slope at 77 K, with respect to 300 K. A new set of compact model parameters for MOSFETs and BJTs under cryogenic temperatures have been extracted. The relative errors between simulation and measurement were below 10% in almost all the bias regions for various device dimensions at 77 K. Two different BGR circuits were designed with the modified compact model parameters and evaluated from 77 K to 300 K. Temperature coefficient of less than 0.2 mV/K has been achieved over the whole range from 300 K to 77 K.